Adds push/pull client functionality

These methods rely on an ObjectStore interface, which is meant to
approximate the storage behavior of the docker engine. This is very much
subject to change.

client/push.go

@@ -0,0 +1,95 @@
+package client
+
+import (
+	"bytes"
+	"crypto/sha1"
+	"io"
+	"io/ioutil"
+
+	"github.com/docker/docker-registry"
+
+	log "github.com/Sirupsen/logrus"
+)
+
+// Push implements a client push workflow for the image defined by the given
+// name and tag pair, using the given ObjectStore for local manifest and layer
+// storage
+func Push(c Client, objectStore ObjectStore, name, tag string) error {
+	manifest, err := objectStore.Manifest(name, tag)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error": err,
+			"name":  name,
+			"tag":   tag,
+		}).Info("No image found")
+		return err
+	}
+
+	for _, fsLayer := range manifest.FSLayers {
+		layer, err := objectStore.Layer(fsLayer.BlobSum)
+		if err != nil {
+			log.WithFields(log.Fields{
+				"error": err,
+				"layer": fsLayer,
+			}).Warn("Unable to read local layer")
+			return err
+		}
+
+		layerReader, err := layer.Reader()
+		if err != nil {
+			log.WithFields(log.Fields{
+				"error": err,
+				"layer": fsLayer,
+			}).Warn("Unable to read local layer")
+			return err
+		}
+
+		location, err := c.InitiateLayerUpload(name, fsLayer.BlobSum)
+		if _, ok := err.(*registry.LayerAlreadyExistsError); ok {
+			log.WithField("layer", fsLayer).Info("Layer already exists")
+			continue
+		}
+		if err != nil {
+			log.WithFields(log.Fields{
+				"error": err,
+				"layer": fsLayer,
+			}).Warn("Unable to upload layer")
+			return err
+		}
+
+		layerBuffer := new(bytes.Buffer)
+		checksum := sha1.New()
+		teeReader := io.TeeReader(layerReader, checksum)
+
+		_, err = io.Copy(layerBuffer, teeReader)
+		if err != nil {
+			log.WithFields(log.Fields{
+				"error": err,
+				"layer": fsLayer,
+			}).Warn("Unable to read local layer")
+			return err
+		}
+
+		err = c.UploadLayer(location, ioutil.NopCloser(layerBuffer), layerBuffer.Len(),
+			&registry.Checksum{HashAlgorithm: "sha1", Sum: string(checksum.Sum(nil))},
+		)
+		if err != nil {
+			log.WithFields(log.Fields{
+				"error": err,
+				"layer": fsLayer,
+			}).Warn("Unable to upload layer")
+			return err
+		}
+	}
+
+	err = c.PutImageManifest(name, tag, manifest)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error":    err,
+			"manifest": manifest,
+		}).Warn("Unable to upload manifest")
+		return err
+	}
+
+	return nil
+}